Three years ago it was Donald Trump who stunned Nato members at a summit in Brussels, warning that he may be prepared to pull the US out of the western military alliance if its other members did not increase their defence spending.At a summit in the same city on Monday, it falls to Joe Biden to repair the damage from four years of his predecessor’s freewheeling theatrics, although experts caution that the Trump era will have lasting consequences.Rhetorically, at least, the omens are favourable. The US president declared Nato’s article 5, under which an armed attack against one member is deemed an attack against them all, a “sacred commitment” last week.Similar language and a respectful tone, long a Biden trademark, are expected in the Belgian capital, not least because the US wants Nato, along with the G7, to take a more robust line against Russia, particularly on cyberwarfare, and even China, not traditionally seen as an opponent.US officials were confidently briefing before the summit that “this will be the first time that the Nato countries will be addressing the security challenge from China”.The alliance’s secretary general, Jens Stoltenberg, has promised a new cybersecurity policy and has said relations with Russia, from where most hacking emanates, were at their lowest point since the end of the cold war.Karin von Hippel, the director general of the Royal United Services Institute thinktank, said: “Biden is arguably the United States’ most experienced foreign policy president. He really does value alliances and knows they are needed to tackle problems like China.“But Nato allies also know that four years can go by pretty quickly in world affairs. They know that Trump, or a politician like him, could return to the presidency soon. They have to imagine a world where the US is not there all the time.”Until Biden’s election, Nato had been paralysed or in retreat. Three years ago, Trump arrived late to a morning session and bulldozed into a discussion about Ukraine’s application for membership and the situation in Afghanistan with a theme of his own.The president accused the German chancellor, Angela Merkel, of refusing to spend more on defence and went on to declare that Nato allies would have to raise their spending by January 2019 or Washington would go it alone.No firm commitments were extracted in the emergency discussion that ensued and most leaders left hastily, but Trump held a press conference and declared, in a parallel universe, that the summit had been a great success. “I’m very consistent. I’m a very stable genius,” he said, repeating an already familiar phrase.Nato officials pared back the 2019 summit in London but Trump ensured it was even shorter anyway, storming out after a group of leaders were caught on video ridiculing his lengthy press conferences. The Canadian prime minister, Justin Trudeau, was two-faced, Trump said, accusing Ottawa of not spending enough on defence.It was almost something of a relief that the coronavirus pandemic intervened in 2020, although Trump ordered the withdrawal of 12,000 US troops from Germany, a decision Biden has reversed. The idea that other Nato members should increase their defence spending and share more of the burden has, however, united a string of US presidents.At the Nato summit in Cardiff in 2014, when Barack Obama was president and Biden his deputy, members agreed to reverse cuts in defence spending and lift it above 2% of GDP. Helped somewhat by falls in GDP related to the pandemic, the UK will hit 2.29% in 2021 and France 2.01%, but Germany’s spending stands at 1.53%.Nor is Biden’s commitment to US militarism absolute. He followed through with Trump’s announcement of a withdrawal from Afghanistan, even though other Nato allies such as the UK would have preferred to continue the long-running peacekeeping mission.Stoltenberg was asked at a press conference on Friday whether Trump’s absence would allow other alliance members to go easy on defence spending. During his reply, he argued that the “transatlantic bond in Nato goes beyond individual political leaders”.Von Hippel, however, cautioned against over-confident talk at what is likely to be an upbeat gathering. “The threat of another Trump should make the Europeans less complacent,” she said. More